1. Field of the Invention
The present invention relates to a bookbinding device and method in which a page stack is bound together with a cover sheet by using hot melt adhesive which is applied to a back surface of the page stack.
2. Prior Art
Many attempts have been made to bind a page stack with a cover sheet by hot melt adhesive applied to a back surface of the page stack into a unitary assembled booklet. In one prior art bookbinding technic, a page stack and a cover sheet are separately transported to a gluing station where a back surface of the page stack, to which hot melt adhesive in a molten condition has been applied during conveyance thereof, is pressed against a center portion of the cover sheet for adhesive binding between the cover sheet and the page stack, followed by folding the cover sheet at lines spaced corresponding to thickness of the page stack for bookbinding into a unitary assembled booklet. In a modified prior art, at a glueing station, a back surface of a page stack is pressed against a center portion of a cover sheet to which hot melt adhesive in a molten state has been applied for adhesive binding of the cover sheet and the page stack. In still another prior art, a center portion of a cover sheet to which a strip of hot melt adhesive is attached is subjected to a heater so that the hot melt adhesive strip is heated to above its melting point, and then a back surface of a page stack is pressed against the center portion for adhesive binding between the cover sheet and the page stack, followed by folding the cover sheet at lines spaced corresponding to thickness of the page stack for bookbinding into a unitary assembled booklet.
A page stack to be bound may have a variety of thickness. According to the above-recited prior arts, a cover width of a resulting booklet will vary depending upon thickness of the page stack, which requires that a cover sheet of a larger size is used in bookbinding and additional steps of trimming the cover sheet depending upon a size of the booklet and dumping the scraps produced after trimming. This will decrease work efficiency and exhaust resources.
Another attempt has been made to provide a set of spaced crease lines on an inside of a central portion of a cover sheet, among which two are selected as folding lines depending upon thickness of a page stack. However, in most case, the selected two lines could not definitely be equal to but is actually somewhat larger than the true thickness of the page stack. Whichever lines are selected, definite alignment between the center of thickness of the page stack and the center of the cover sheet could not be achieved. Further, this prior art also has a drawback which have been described in connection with the afore-mentioned prior arts so that a cover width of a resulting booklet varies depending upon thickness of the page stack.
In a device disclosed in Japanese patent publication No. 6-43152, crease lines spaced in conformity to thickness of a page stack is formed on a center portion of a cover sheet, and a continuous sheet of hot melt adhesive is cut into a strip of width corresponding to the thickness of the page stack, which is placed between the spaced crease lines on the center portion of the cover sheet or alternatively on a hot plate. The hot melt strip is then heated to above its melting point so that a back surface of the page stack is bonded to the center portion of the cover sheet.
With this device, the crease lines are spaced conforming to the thickness of the page stack, so that definite alignment or centering between the cover sheet and the page stack in a resulting booklet can be achieved. This prior art, however, provide no solution to a problem that a cover width of a resulting booklet varies depending upon thickness of the page stack and, therefore, requires post-bookbinding step of trimming at least one side edge of the cover sheet and a subsequent dumping step.
The above-recited prior art device is provided with a lever handle which may be automatically operated to cut the hot melt adhesive sheet into a strip having a predetermined width corresponding to the thickness of the page stack, Yet, a subsequent step of placing the cut sheet or strip onto a predetermined platform is not automated, which requires manual operation to pick up the hot melt adhesive strip and move it onto the platform. This means that the device can not provide fully-automated bookbinding operation. Moreover, the hot melt adhesive strip tends to be offset from a predetermined position on the platform. Even if it is once placed in position, it may be displaced or moved during operation of the device. Accordingly, it is desirable that a pressure-sensitive adhesive layer or the like is formed on the underside of the hot melt adhesive sheet to prevent displacement of the hot melt adhesive strip on the platform before melt by heating, which increases production cost.
A title indicating the contents of the booklet or any decorative image is often printed beforehand on a cover sheet, which is supplied to a bookbinding device. In accordance with the prior art bookbinding technic, however, as described before, a center line in width of a cover of a resulting booklet varies depending upon thickness of a page stack so that the printed title or image may appear on the cover in an offset position. Such offset positioning becomes remarkable and looks unattractive when a cover has a full-page print.
To produce booklets with beautiful appearance, it is necessary to jog back edges of pages to be bound during conveyance of the page stack. While such jogging device is disclosed in some prior arts including Japanese patent publication Nos. 60-191956, 5-77585, 5-77579, 8-12174, 10-203714 and Japanese utility model publication No. 63-90658, none of them could not provide uniform jogging effect where thickness of the page stack is varied.
Accordingly, it is a primary object of the present invention to overcome the drawbacks and disadvantages of the prior art bookbinding technic and provide a novel bookbinding device and method which involves cutting a cover sheet depending upon thickness of a page stack to be bound so that a cover of a resulting booklet should always agrees with a width size of the page stack, which may omit a post-bookbinding cover-cutting.
Another object of the present invention is to provide a bookbinding device with a jogger capable of providing uniform and sufficient jogging effect even when the page stack has varying thickness.
To achieve these and other objects, according to an aspect of the present invention, there is provided a bookbinding device comprising a page supply unit for supplying a stack of pages to be bound to a predetermined first station, the page stack being kept in a clamped condition from opposite sides thereof; a thickness sensor for detecting thickness of the clamped page stack during supply thereof by the page supply unit; an adhesive applicator for applying molten adhesive to a back surface of the page stack at the first station; a page conveyor unit for conveying the page stack with the glued back surface from the first station to a second station remote from the first station; a cover supply unit for supplying a cover sheet to beneath the glued back surface of the page stack at the second station; a press unit for contacting under pressure the glued back surface of the page stack with a center portion of the cover sheet for adhesive binding therebetween; and a cover folding unit for folding the cover sheet substantially along opposite side edges of the page stack to form a unitary assembled booklet; the cover supply unit including a trimmer for trimming a side edge portion of the cover sheet depending upon thickness of the page stack detected by the thickness sensor, and a positioning unit for positioning the cover sheet such that a center line of the cover sheet which has been trimmed by the trimmer is aligned with a center of thickness of the page stack at the second position.
The bookbinding device may further comprise a scrap discharging unit for discharging scraps produced after the trimmer trims the side edge portion of the cover sheet, through a scrap chute that is independent from a cover sheet travel path defined by the cover supply unit. Preferably, a changeover switch is arranged just beneath the trimmer, which is regulated in synchronism with operation of the trimmer so as to guide the scrap into the scrap chute and guide the trimmed cover sheet to feed along the cover sheet travel path.
The bookbinding device may further be provided with a printer unit arranged along the cover sheet travel path between the trimmer and the second station for printing any desired image on the cover sheet.
The page supply unit preferably comprises a clamper for clamping the page stack from opposite sides thereof; a release mechanism for unclamping the page stack at a jogging station where the page stack is kept substantially upstanding or slanting; a holder unit with a bottom support for supporting a bottom edge of the page stack when the page stack is unclamped by the release mechanism; a first vibration generator for vibrating the holder unit in up-and-down directions to jog the bottom edge of the page stack; a second vibration generator for vibrating the page stack in its width directions to jog opposite side edges of the page stack; and a spring-biased press member for press- and resilient-contact with a top edge of the page stack while being vibrated in up-and-down directions by the first vibration generator.
In this embodiment, the holder unit may comprise a base to which the bottom support is fixed, and a second bottom support slidably connected to the base. The bottom support provides a supporting surface positioned between an uppermost position and a lowermost position of the elevatable second bottom support. The second bottom support is vibrated by the first vibration generator.
In another embodiment, the holder unit comprises a stationary guide member for definitely positioning a first side edge of the page stack and a movable guide member adapted to provide resilient contact with a second side edge, opposite to the first side edge, of the page stack. In this embodiment, the second vibration generator may comprise a swingable arm with a contact surface opposing to the second side edge of the page stack, and an actuator for swinging the arm so that the contact surface intermittently collides against the second side edge of the page stack.
According to another aspect of the present invention, there is provided a bookbinding device comprising a clamper for clamping the page stack from opposite sides thereof; a release mechanism for unclamping the page stack at a jogging station where the page stack is kept substantially upstanding or slanting; a holder unit with a bottom support for supporting a bottom edge of the page stack when the page stack is unclamped by the release mechanism; a first vibration generator for vibrating the holder unit in up-and-down directions to jog the bottom edge of the page stack; a second vibration generator for vibrating the page stack in its width directions to jog opposite side edges of the page stack; and a spring-biased press member for press-contact with a top edge of the page stack while being vibrated in up-and-down directions by the first vibration generator.
The holder unit may comprise a base to which the bottom support is fixed, and a second bottom support slidably connected to the base. The bottom support provides a supporting surface positioned between an uppermost position and a lowermost position of the elevatable second bottom support. The second bottom support is vibrated by the first vibration generator.
In another embodiment, the bookbinding device unit further comprises a stationary guide member for definitely positioning one side edge of the page stack and a movable guide member adapted to provide spring-biased contact with the other side edge of the page stack. In this embodiment, the second vibration generator may comprise a swingable arm with a contact surface opposing to the other side edge of the page stack, and an actuator for swinging the arm so that the contact surface intermittently collides against the other side edge of the page stack.
According to still another aspect of the present invention, there is provided a bookbinding method comprising the steps of supplying a stack of pages to be bound to a first station, the page stack being kept in a clamped condition from opposite sides thereof; detecting thickness of the clamped page stack during supply thereof; applying molten adhesive to a back surface of the page stack at the first station; conveying the page stack with the glued back surface from the first station to a second station remote from the first station; trimming a side edge portion of a cover sheet depending upon thickness of the page stack; supplying the cover sheet with the trimmed side edge portion to beneath the glued back surface of the page stack such that a center line of the cover sheet is aligned with a center of thickness of the page stack at the second position; contacting under pressure the glued back surface of the page stack with the cover sheet for adhesive binding therebetween; and folding the cover sheet substantially along opposite side edges of the page stack to form a unitary assembled booklet.